. Biophysics: concepts and mechanisms. Biophysics. PROPERTIES OF MATTER WAVES 51 Amplitude and Intensity There is a minimum pressure and power of matter waves below which the ear cannot detect the wave. This value is about dynes/cm2, an ex- tremely small value because the ear is very sensitive. The corresponding power or intensity limit is ~10 9 ergs/cm2 sec, , ^lO"16 w/cm2! This value places its sensitivity very close to the threshold of the power in heat motion, and thus very close to the minimum background agitation of matter in our environment. The maximum amplitude the ear
. Biophysics: concepts and mechanisms. Biophysics. PROPERTIES OF MATTER WAVES 51 Amplitude and Intensity There is a minimum pressure and power of matter waves below which the ear cannot detect the wave. This value is about dynes/cm2, an ex- tremely small value because the ear is very sensitive. The corresponding power or intensity limit is ~10 9 ergs/cm2 sec, , ^lO"16 w/cm2! This value places its sensitivity very close to the threshold of the power in heat motion, and thus very close to the minimum background agitation of matter in our environment. The maximum amplitude the eardrum can stand, with- out certain irreparable damage resulting, is ~200 dynes/cm2. Therefore, the range of sensitivity of the ear is phenomenally high, one to a million. It is the most sensitive at 1,000 cps. The sense of touch, particularly on the fingers and tongue, is not nearly so sensitive, but responds down to much lower frequencies. To our knowledge, man has no detection apparatus for frequencies above about 20,000 cps. However, there is some evidence that ultrasound can penetrate to the brain and cause psychological aberrations, which may or may not be a result of organic damage. One of the most convenient ways of generating matter waves of controlled frequency is by means of the vibrating crystal. Certain crystals are piezo- electric—that is, they expand or contract if an electric voltage is applied to contacts with two different crystal faces (Figure 3-2). The amount of the (o) £l_ + V volts. crystol (b) applied voltage, V (c). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Casey, Edmund Jeremiah, 1924-. New York, Reinhold Pub. Corp
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